Engine-driven generator speed control system and method

ABSTRACT

A system and method are provided for controlling an internal combustion engine driving a generator/welder or a stand-alone generator. Controlling the engine may include altering the engine speed based upon a detected demand on the generator and/or operating parameters of a welder. For example, the engine speed may be increased based on a detected draw on the generator and/or the operating parameters of the welder. In addition, the engine speed may be automatically decreased to a non-standard idle speed or the engine may be automatically turned off if no demand is detected for a period of time. Additionally, the engine speed may be increased if only frequency-insensitive demands are detected on the generator. Combinations of these and further methods may be executed. Various devices are provided for implementing the above methods.

BACKGROUND

The invention relates generally to a system and method for controllingan engine driving a generator based on engine conditions and generatorload.

Engine-driven generators are commonly used to provide electrical powerin locations where conventional electrical power is not readilyavailable. Both gasoline and diesel engines are used to drive suchgenerators, and the power produced is typically either 120 VAC or 240VAC. An engine-driven generator may be used to supply power to a weldinggun (e.g., torch, arc, or the like) for applications such as, forexample, stick electrode welding, MIG welding, TIG welding, etc. Thesewelding systems include a control system to regulate the power producedby the generator, thereby making it suitable for arc welding, plasmacutting, and similar operations.

Typical welding systems offer the user little customizable control overthe engine settings. For example, the engine may employ an enginegovernor to control the engine speed. When the welding gun or anauxiliary device is connected to the system and turned on, the enginespeed may increase to the speed required to power the load. This speedincrease may be determined by a generic governor curve which slowlyincreases the engine speed to substantially prevent overshooting therequired speed. No distinction is made between the weld load and theauxiliary load, such as a light, which may require significantly lesspower to operate than the welder.

In addition, during periods of non-use of the typical welding system,the engine speed may be reduced to an idle speed. However, this idlespeed may still consume a great deal of energy and produce substantialnoise levels. A user may have no choice but to endure theseinconveniences or to manually turn the engine off when it will not beused for some time. The engine must then be manually restarted beforethe welding gun may be used again.

BRIEF DESCRIPTION

In accordance with certain aspects of the invention, a method forcontrolling an engine-driven generator/welder includes monitoring for avoltage and/or current draw on welding and auxiliary outputs of thegenerator, and controlling the speed of the internal combustion enginebased upon the detected draw.

There is further provided a method for controlling an engine-drivengenerator/welder, including monitoring for a demand on a welding outputof the generator, increasing the speed of the internal combustion engineusing a custom control regime based on preset operating parameters whenthe demand is detected, and transitioning to an engine speed controlregime based upon the engine speed.

The invention also provides an engine-driven generator/welder system,including an internal combustion engine, a generator driven by theinternal combustion engine, and a controller configured to detect a welddemand on the welding power generator and to control the internalcombustion engine at least in part based upon the detected weld demandand/or preset operating parameters.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a diagrammatical overview of an integrated engine andgenerator control scheme in accordance with certain aspects of theinvention, permitting improved control of engine and generatorfunctions;

FIG. 2 is a block diagram of an engine-driven generator/welder systemaccording to an embodiment of the present invention;

FIG. 3 is an engine speed graph according to an embodiment of thepresent invention;

FIG. 4 is a flow chart illustrating an engine control process forproducing a series illustrated in the engine speed graph of FIG. 3according to an embodiment of the present invention;

FIG. 5 is a flow chart illustrating a further engine control process forproducing another series illustrated in the engine speed graph of FIG. 3according to an embodiment of the present invention;

FIG. 6 is another engine speed graph according to an embodiment of thepresent invention;

FIG. 7 is a flow chart illustrating another engine control process forproducing a series illustrated in the engine speed graph of FIG. 6according to an embodiment of the present invention;

FIG. 8 is a flow chart illustrating still another engine control processfor producing yet another series illustrated in the engine speed graphof FIG. 6 according to an embodiment of the present invention;

FIG. 9 is a further engine speed graph according to an embodiment of thepresent invention;

FIG. 10 is a flow chart illustrating yet another engine control processfor producing a series illustrated in the engine speed graph of FIG. 9according to an embodiment of the present invention; and

FIG. 11 is an engine speed graph produced via a combination of theengine control processes illustrated in FIGS. 4, 5, 7, and 9 accordingto an embodiment of the present invention.

DETAILED DESCRIPTION

The present invention relates to control of an engine driving anelectrical generator. An engine powering a generator/welder may includecontrols which affect the engine speed, ignition, fuel injection, sparktiming, and any other controllable parameter of the engine based onvarious inputs. Such inputs may include, for example, currents orvoltages supplied to loads, such as a welding gun and/or an auxiliarydevice, preset welding parameters, and time.

FIG. 1 is a diagrammatical overview of an exemplary integrated engineand generator control scheme in accordance with aspects of the presentinvention. As described in greater detail below, the system can beapplied to a range of engines, such as gasoline engines and dieselengines. Moreover, the engine may include a wide range of measurable,observable and controllable parameters, such as, by way of example only,fuel flow, throttle position, speed, torque, power, spark advance (e.g.,for gasoline engines), and so forth. Certain of these controls may beimplemented mechanically, electromechanically or electronically, such asthrough the use of an electronic governor. In general, the engine willbe started and will operate at speeds as determined by an integratedcontroller illustrated in FIG. 1. The integrated controller can causethe engine to operate at particular speeds depending upon optimaloperating conditions, draw by particular loads, as summarized in greaterdetail below, and so forth.

In the embodiment illustrated in FIG. 1, the engine will drive agenerator. Indeed, while the generator represents a load for the engine,the generator is, itself, a power source for electrical loads. In thediagrammatical illustration of FIG. 1, other electrical power sourcesmay also be included in the system, such as batteries, grid convertersconfigured to draw power from an electrical grid and to provide it toelectrical loads. In certain presently contemplated systems, thegenerator will operate in parallel with other electrical power sourcessuch as batteries and grid converters. In terms of the engine operation,the loads are drawing electrical power from the generator, and/or otherelectrical power sources, can influence the control of the engine by theintermediary of the integrated controller. Thus, electrical parametersmay be sensed for the generator, batteries, grid converters, and otherelectrical power sources and the integrated controller may use thesesensed parameters to control the operation and performance of theengine. It should also be noted that the integrated controller may alsoregulate certain functions of the electrical power sources. For example,the controller may regulate a field of the generator so as to controlpower production by the generator in accordance with needs of electricalloads and coordinated with speed and torque control of the engine. Inpresently contemplated applications, the electrical power sources willgenerate controlled electrical power which is available for a variety ofloads. The electrical power may be a function of the speed at which theengine turns the generator and the number of poles included in thegenerator, or this power may further processed as described below.

FIG. 1 also illustrates a number of exemplary loads that may drawelectrical power from the electrical power sources, including theengine-generator set. In the presently contemplated embodiments, theseinclude a welder and certain auxiliary loads. As will be appreciated bythose skilled in the art, the welder requires significant power forcreation of electrical arcs used to fuse metals in welding operations.The welder illustrated in FIG. 1 may convert power from the generator topower appropriate for the particular welding operation to be performed.As also described below, such welding operations may require constantvoltage output regimes, constant current regimes, or various pulsedregimes, depending upon the nature of the welding operation. Auxiliaryloads may include both alternating current and direct current loads,with output from the power sources being converted as necessary for theparticular loads. In certain embodiments, the integrated controller mayoperate the engine at appropriate speeds and power levels to accommodateboth welding loads and auxiliary loads. For example, tools, lights, andother loads designed to operate on alternating current at frequencies ofa power grid (e.g., 60 Hz in North America) may require the engine tooperate at specific speeds, depending upon the number of pulls of thegenerator. The integrated controller may sense output of the generatorand output of the loads, or draw by the loads to regulate engine speedaccordingly.

Other loads that may be powered by the system illustrated in FIG. 1 mayinclude a battery charger. In many mobile applications, for example, itmay be useful to drive the engine as an auxiliary power source to chargea vehicle battery. Several other loads are also illustrated in FIG. 1,by way of a non-exhaustive list. Such other loads may include plasmacutters, wire feeders, alternating current sources used for specificoperations, such as tungsten inert gas (TIG) welding, various weldingaccessories, power converters, such as inverters and choppers, and soforth. As with the welder and the auxiliary loads discussed above, theintegrated controller may coordinate operation of the engine and/orgenerator to accommodate such loads based, for example, upon detectionof connections, power draw, signatures of particular tools, and soforth.

The integrated controller may also take into account for control of theengine and/or generator, inputs from a variety of sources, several ofwhich are listed in the diagram of FIG. 1. Presently contemplatedsources for control include various operator inputs. Such operatorinputs may be included in a control panel or human interface on thewelders/generator cabinet. By way of example, operator inputs may setweld parameters as discussed below. However, operator inputs may alsoinclude manual override of speeds, manual input of desired noise or fuelusage, and so forth. Inputs may also be networked as illustrated inFIG. 1. Such networked inputs may include, for example, inputs receivedvia a dedicated network connection, a LAN connection, a WAN connection,wirelessly, and so forth. Indeed, any of the inputs or even controlledparameters are regulated by the integrated controller may be input by anoperator or by a network. Other input sources may include commands orrequests for specific power or electrical parameters from any one of theloads coupled to the electrical power sources. Such inputs may furtherinclude devices coupled directly or indirectly to the engine and notthrough the electrical power sources. For example, in certainapplications the engine may drive other devices (not shown in FIG. 1)such as air compressors, hydraulic pumps, and so forth, and theintegrated controller may receive inputs indicating that such devicesare active and join power from the engine, and alter the engine speed,fuel flow rate, output torque or power, and so forth based upon suchinputs.

The integrated controller itself may take any suitable form, and willtypically include one or more power supplies and one or more processorswith associated memory for storing sensed parameter values, controlprograms, and so forth. Because the system, in many applications, willbe mobile, the integrated controller will typically be packaged in arobust manner capable of operation in difficult environmental conditionsalong with the engine, generator, and other components of the system.The processor may include any suitable digital processor, such asmicroprocessors, field programmable gate arrays, and so forth. Memorydevices may be provided as part of the processor package, such as in thecase of a field programmable gate array, an additional memory mayinclude flash memory, random access memory, read only memory,programmable read only memory, and so forth. The control routines forregulating operation of the engine and the generator may be written inany suitable computer language, and such code is considered to wellwithin the ambit of those skilled in the art based upon the variouscontrol regimes discussed below.

The degree of integration of control implemented by the integratedcontroller may vary depending upon the sophistication of the controlregimes envisaged. For example, as described in greater detail below,the integrated controller may sense certain electrical parameters of thepower sources, and particularly those of the generator, and performrelatively simple operations, such as speed control based on throttlepositions, fuel flow rate, and so forth for the engine. Much moresophisticated control regimes may, however, be implemented in which thecontroller regulates both parameters of the engine and parameters of thegenerator to accommodate particular loads and power needs.

As discussed above, depending upon the engine design, the generatordesign, and the anticipated loads, the integrated controller may performvarious functions specifically adapted for those machines. In certainpresently contemplated applications, for example, many functions of theengine may be controlled mechanically, and the engine may be based uponcarborated fuel mixing. In other applications, the engines will includefuel injected versions. Mechanical or electronic governors may beaccommodated, with carborated fuel mixing or fuel injection. As will beappreciated by those skilled in the art, for mechanical governors, thecontroller generally will not control the throttle position. Similarly,engines in the system may be single cylinder, twin cylinder, threecylinder or more, and may be liquid or air cooled.

As also mentioned above, control may be based upon the particular designof the generator and any other electrical power sources in the system.For example, in certain presently contemplated designs, the generatormay employ an electrical rheostat for field control. Such field controlmay be regulated by the integrated controller. In such applications, theintegrated controller may also control injectors for the engine, and allof such control may be based upon inputs from a welder, auxiliary loadsof various types, and so forth.

FIG. 2 illustrates an engine driven welding and power generating system10 in accordance with an embodiment of the present invention. The system10 generally includes an engine 12, a weld generator 14, and a generator16 for providing auxiliary power output. An integrated control systemincludes an engine controller 18 and a welder controller 20, which canbe fully or partially integrated to receive inputs for control from theengine, the weld generator and the auxiliary generator, and produceoutputs for control of the engine, the generator, or both. The weldgenerator provides power for a welder 22, which may be controlled by theweld controller 20. The welder will typically include a welding gun(e.g., a MIG or TIG torch, stick handle, etc.). Various auxiliary loadsor devices 24 (e.g., lights, power tools, radios, etc.) may be poweredby power from the auxiliary generator 16. The engine 12 may be agasoline or diesel engine which drives the generators.

As illustrated in FIG. 2, the controller 18 may receive inputs from theengine 12, a user interface 52, and/or power outputs from thegenerators. For example, sensors disposed within or coupled to theengine 12 may provide engine information to the controller 18 relatingto engine operating conditions, settings, transient conditions, and soforth. Exemplary sensors may include a temperature sensor 26, an oxygensensor 28, a manifold pressure sensor 30, an RPM sensor 32, a crankposition sensor 34. Further engine sensors may detect informationregarding the throttle position, the fuel injection rate, the sparktiming, mass air flow rate, and so forth. In addition, sensors coupledto the one or more power outputs of the generators 14 and 16 may provideinformation about loads drawing power from the generators (e.g., thewelder 22 and/or the auxiliary loads 24). For example, a voltage sensor36 and/or a current sensor 38 may be coupled to power output lines ofthe generator 14 to enable the controller to determine whether a load(e.g., welder 22) is drawing power from the generator, and the level ofpower draw. Similarly, a voltage sensor 40 and/or a current sensor 42may be coupled to power output lines of generator 16 to detect drawsfrom that generator. User inputs (e.g., preset operating parameters) mayalso be supplied to the controller via the user interface 52. Exemplarypreset operating parameters may include current and voltagerequirements, process type (e.g., constant current, constant voltage,MIG, TIG, stick), wire electrode or stick size, and so forth. The userinterface 24 may be integral with the system or may be an independentdevice, such as, for example, an input panel, a remote control system,and so forth. The user interface 24 may include, for example, a userinput device such as a keypad, a keyboard, a mouse, a touch-screen,dials, switches, potentiometers, LEDs, lights, etc., and a display, suchas a monitor, a CRT display, an LCD screen, etc.

In addition to receiving engine, process, and load information frominputs, the controller may send control signals to various enginesystems. As described in more detail below, the controller may processsome or all of the information gathered from the sensors 38-42 and/orinput via the user interface 52 to alter engine operation settings. Forexample, the controller may manage an engine governor 44 (e.g., via athrottle plate), the ignition or crank timing 46, a fuel injector 48 andits timing, a spark timer 50, or any other engine component which may becontrolled. To process all of the signals input to and output from thecontroller, the controller may, for example, include discrete analogand/or digital circuits, a logic device, a microprocessor, amicrocontroller, a programmable logic controller, a field-programmablegate array, a complex programmable logic device, etc.

FIG. 3 is a graph 54 of generator speed 56 (e.g., revolutions perminute) versus time 58 in accordance with embodiments of the presentinvention. Referring generally to FIG. 2 for the components of system 10and to FIG. 3 for the graph 54, an idle speed 60 may be around 1800-2400rpm for an internal combustion engine such as a two-cylinder gas engine.In another embodiment, a diesel engine may operate with an idle speedaround 600-1200 rpm. The engine 18 powering the weld generator 14 andthe auxiliary generator 16 may operate at an operating speed 62.Generally, the normal operating speed 62 is the engine speed at which asynchronous power output frequency is produced. American devicestypically utilize a 60 Hz frequency, and other devices utilize a 50 Hzfrequency. The normal operating speed 62 of an exemplary two-cylindergas engine may be about 3600 rpm, producing an alternating current witha frequency of about 60 Hz. An engine-driven four-pole generator mayproduce a 60 Hz frequency at about 1800 rpm. The engine operating speed62 may be approximately based on the following equation:

$\begin{matrix}{{s = \frac{120f}{P}},} & (1)\end{matrix}$

where s is the speed of the engine (rpm), f is the target frequency(Hz), and P is the number of poles in the generator. Other idle andoperating speeds 60 and 62 may be used depending, for example, on theengine type (e.g., gasoline or diesel) and the engine design (e.g.,number of cylinders, number of poles, etc.).

A trace 64 illustrates ramp-up of the engine speed 56 from the idlespeed 60 to the operating speed 62 as observed in traditional enginecontrol systems. For example, the welder 22 and/or the auxiliary load 24may be turned on at a time 66. Due to the increase in required torquewhen the engine load is increased, the speed 56 of the engine 12initially decreases. After some time, the engine governor 44 detects thechange in the engine speed 56 and increases the fuel flow rate toincrease the engine speed 56 to compensate for the increased load. Theengine speed 56 then increases to the operating speed 62 based on agovernor curve. A traditional rpm-based control regime may utilize ageneric governor curve to ramp up the engine speed 56 to the requiredspeed for a given load (and to maintain the speed in an rpm-closedloop). That is, the engine speed 56 is ramped up relatively slowly sothat the required speed for a given load is not greatly surpassed (i.e.,to limit “overshoot”). To reach and maintain the operating speed 62, thecontroller may employ various control techniques, such as, for example,closed-loop control, open-loop control, PID control, direct poleplacement, optimal control, adaptive control, intelligent control,non-linear control, etc. After a time 68, the engine speed 56 isgenerally constant at the operating speed 62. As can be seen in thegraph 54, the trace 64 exhibits a significant droop after the load isintroduced before the governor 44 begins to ramp up the engine speed 56.

In contrast, a trace 70 illustrates an improved technique for ramping upthe engine speed 56 when the welder 22 draws power from generator 14. Auser may input settings, such as the required current and voltage forthe welder 22, via the user interface 52. The controller may then sensewhen the welder 22 is operative by monitoring the drawn voltage andcurrent via the sensors 36 and 38 on the welding power output. Upondetection of a draw on the generator 14, the controller may send asignal to the engine governor 44 to immediately begin ramping up theengine speed 56 based on a modified governor curve. For example, theuser-input settings may be utilized in a lookup table, an algorithm,etc. to determine the governor curve which most efficiently increasesthe engine speed 56 to the desired operating speed 62. The controller 22may store information on any number of input-specific governor curves inaddition to the generic governor curve. When the welder 22 begins todraw power at the time 66, the engine speed 56 may decrease brieflyunder the load. However, because a signal is sent to the engine governor44 as soon as the draw is detected, the governor 44 begins ramping upthe engine speed 56 much faster than in the traditional engine controlsystem illustrated by the trace 64. Therefore, the engine speed 56 maybe generally constant at the operating speed 62 after a time 72. Thedelay from the onset of engine loading to the time 72 may besignificantly less than that to the time 68 (traditional control) atwhich the trace 64 maintains the operating speed 62.

Furthermore, the controller may employ different control regimes atdifferent times in the ramp-up and speed maintaining process. Forexample, trace 70 illustrates a preset-based control regime furtherillustrated in FIG. 4. In contrast, trace 64 illustrates a traditionalrpm-based control regime. As can be seen in the graph 54, thepreset-based control regime (trace 70) could overshoot the operatingspeed 62 to a greater extent than the rpm-based control regime (trace64). This phenomenon may be attributed to the techniques employed by therespective control regimes in increasing the engine speed 56. To combinethe increased speed ramp-up in the preset-based control regime with thestabilization of the rpm-based control regime, the controller may switchfrom one control regime to the other, such as depending on the enginespeed 56. For example, at a time 74, as the engine speed 56 approachesthe target operating speed 62 using the preset-based control regime(trace 70), the controller may switch to the rpm-based control regime(trace 64). By changing control regimes, the benefits of each type ofcontrol may be optimized.

FIG. 4 illustrates a process 76 by which the trace 70 (FIG. 3) may begenerated. Referring to FIG. 2 for the components of system 10, to FIG.3 for the graph 54, and to FIG. 4 for the process 76, preset operatingparameters may be input (block 78), such as via the user interface 52.The preset operating parameters may include, for example the current andvoltage required by the welder 22, a welding regime, details of theregime, etc. The engine load may then be determined based on the inputsettings for the welder 22 (block 80). That is, the idle speed 60, theoperating speed 62, and/or the anticipated load to achieve the requisitecurrent and voltage outputs for the welder 22 may be determined. Forexample, a lookup table, an algorithm, etc. may be utilized to determinethe engine load, the idle speed 60, and/or the operating speed 62required for the load. These may be determined empirically, a priori, bytesting of the engine under anticipated load conditions. After theoperating parameters are input, the engine 12 may idle for a period oftime (block 82), for example, while the user prepares the welder 22.When the welder 22 becomes operative (e.g., an arc is struck), thecontroller senses a draw on the generator 14 (block 84). The controllermay then send a signal to the engine governor 44, ignition/crank input46, the fuel injector 48, the spark timer 50, etc., to begin ramping upthe engine speed 56 from the idle speed 60 to the operating speed 62(block 88). The ramp-up process may utilize an engine governor curvebased on the user input settings and the anticipated operating speed 62.For example, if the welder 22 requires output power that is generatedwhen the generator operates at a speed 62 of 3600 rpm, the controllermay adjust the engine operating settings to open the engine throttle tothe requisite position for operating the engine at 3600 rpm. The enginethen quickly ramps up to the operating speed 62.

FIG. 5 illustrates a process 90 by which the engine control regime maybe changed. Referring to FIG. 3 for the graph 54 and to FIG. 4 for theprocess 90, the engine speed 56 may ramp up using the preset-basedcontrol regime (block 92). The engine speed 56 may then be monitored(block 94) and compared to the target operating speed 62 (block 96). Ifthe engine speed 56 is not near the operating speed 62, the ramp upcontinues using the preset-based control regime (block 92). However, ifthe engine speed 56 is near the operating speed 62, the rpm-basedcontrol regime may be implemented (block 98). The threshold after whichthe engine speed 56 may be considered “near” the operating speed 62 maybe a preset value, a user-input value, a percentage of the operatingspeed 62, or another appropriate level.

FIG. 6 is a graph 100 of the engine speed 56 versus the time 58 inaccordance with embodiments of the present invention. Referringgenerally to FIG. 2 for the system 10 components and to FIG. 6 for thegraph 100, in addition to the idle speed 60 and the rated speed 62, alow idle speed 102 and an engine off speed 104 (i.e., stopped) areillustrated. For example, an engine with an idle speed 60 of 1800 rpmmay have a low idle speed 102 of around 1600 rpm, although other lowidle speeds 102 may be implemented. Reducing the engine speed 56 orturning the engine off during non-use serves to cool the engine and toreduce noise and fuel consumption when not servicing a load. In anotherembodiment, a high idle speed 105 may be implemented to anticipatedemand of the welder 22 based on preset operating parameters. Forexample, if the engine has an idle speed 60 of 1800 rpm and a presetoperating speed 62 of 3600 rpm, the high idle speed 105 may beapproximately 3000 rpm. The high idle speed 105, for example, may enablea faster increase to the operating speed 62 when the engine idlesintermittently.

Traces 106, 108, and 114 illustrate possible energy-saving techniqueswhich may be implemented in the system 10. For example, if there is nodraw on the generators after a time 110, the engine speed 56 maydecrease from the idle speed 60 to the low idle speed 102 (trace 106),or operation of the engine may be temporally interrupted (trace 108),reducing the engine speed 56 to the engine off speed 104. Upon detectionof a draw on the engine at a time 112, the engine speed 56 may ramp upto the operating speed 62 using any of the control techniques discussedabove. Furthermore, a combination of the low idle speed 102 and theengine off speed 104 may be employed, as illustrated by a trace 114. Forexample, the engine speed 56 may decrease to the low idle speed 102after the time 110 and may then decrease to the engine off speed 104after a time 116.

In another embodiment, the engine speed 56 may initially decrease fromthe operating speed 62 to the high idle speed 105. Upon detection of adraw on the generators, the engine speed 56 may return to the operatingspeed 62. However, if there is no draw detected after the time 110, theengine speed 56 may decrease from the high idle speed 105 to a lowerspeed (e.g., the idle speed 60, as illustrated by the trace 109; the lowidle speed 102; the engine off speed 104; or another engine speed 56).It should be noted that the times 110, 112, and 116 may be different fordifferent idle regimes. For example, it may be desirable to maintain theengine at the high idle speed 105 for a shorter period of time than forthe idle speed 60 before transitioning to a lower engine speed 56.

Turning to FIG. 7, a process 118 by which the traces 106, 108, and 114(FIG. 6) may be generated is illustrated. Referring to FIG. 2 for thesystem 10 components, to FIG. 6 for the graph 100, and to FIG. 7 for theprocess 118 steps, the engine 18 may operate at the high idle speed 105or the idle speed 60 (block 120). The controller may monitor the currentand voltage draws on the power outputs to determine if a load is drawingon the generators (block 122). If there is no draw, the engine speed 56may be decreased to the idle speed 60 (e.g., from the high idle speed105), to the low idle speed 102 (e.g., from the idle speed 60 or thehigh idle speed 105), or to the engine off speed 104 (e.g., from theidle speed 60, the low idle speed 102, or the high idle speed 105)(block 124). After the engine speed 56 decreases, the controller maycontinue to monitor the current and/or voltage from the generators viathe sensors 36-42 (block 126). If either the welder 22 or the auxiliaryload 24 draws a current and/or voltage, the engine may restart and/orthe engine speed 56 may be ramped up to the operating speed 62 (block128). In addition, a switch may be used to restart the engine aftershutdown. For example, the welder 22 may include a switch so that theengine can be started remotely. If there is no draw on the generators,the engine speed 56 may remain at the idle speed 60 or the low idlespeed 102, or the engine may remain off (block 124). It should be notedthat while four idle/off speeds are illustrated in the graph 100 (FIG.6) and the process 118 (FIG. 7), any number and/or combination ofidle/off speeds may be implemented in accordance with the presentdisclosure.

FIG. 8 illustrates a process 130 which incorporates multiple reductionsin the engine speed 56, as illustrated by the trace 114 (FIG. 6).Referring to FIG. 2 for the system 10 components, to FIG. 6 for thegraph 100, and to FIG. 8 for the process 130 steps, the engine may idleat the idle speed 60 (block 132). The controller may monitor the enginespeed 56 and/or the current and voltage draws on the generators todetermine how long the engine has been at idle (block 134). If theengine 18 has not been at idle for the predetermined time, the enginespeed 56 may remain at the idle speed 60 (block 132). However, if theengine has been at idle for a predetermined time, the engine speed 56may decrease to the low idle speed 102 (block 136). The controller maythen continue to monitor the engine speed 56 to determine how long theengine has been at the low idle speed 102 (block 138). If the engine hasnot been at the low idle speed 102 for the predetermined time, theengine speed 56 may remain at the low idle speed 102 (block 136). If theengine has been at the low idle speed 102 for a predetermined time, theengine may be temporally shut off, decreasing the engine speed 56 to theengine off speed 104 (block 140). After the engine shuts down, thecontroller may continue to monitor the sensors 36-42 for a load (block142). If either the welder 22 or the auxiliary load 24 is turned on(i.e., begin to draw power, or demand power), the engine 18 may restartand the engine speed 56 may be ramped up to the rated speed 62 (block144). In addition, a switch may be used to restart the engine aftershutdown. For example, the torch 20 may include a switch so that theengine can be started remotely. If no load is detected, the engine mayremain off (block 140). It should be understood that differentcombinations of idle speeds may be implemented in the process 130, andany number of speeds may be employed to implement a gradual reduction inthe engine speed 56.

Turning to FIG. 9, a graph 146 of the engine speed 56 versus the time 58is illustrated in accordance with embodiments of the present invention.FIG. 2 is generally referred to for the system 10 components, and FIG. 9is referred to for the graph 146. In this aspect of the presentinvention, an “intelligent overspeed” 148 may be implemented to improvepower output for welding, particularly when an auxiliary load 24 is notdrawing power from generator 16 or is not sensitive to the frequencysupplied by the generator 16. It may be desirable to increase the speed56 of the engine, and therefore the output of the generator 14, whenperforming high-amperage processes, such as, for example, gouging, wirewelding with a large wire, stick welding with a large stick, orprocesses involving multiple inverters. A trace 150 illustrates the useof the intelligent overspeed 148. At a time 152, the engine speed 56 maybe increased from the normal operating speed 62 to a higher speed 148.The higher speed 148 may be an engine speed 56 at which the welder 22operates more efficiently (e.g., 3700-3800 rpm for a 2-pole gasolineengine, or 2400-3000 rpm for a 4-pole diesel engine). Other speeds 148may be implemented depending on the operating parameters of the systemand the welder 22. In addition, the speed 148 may be a preset value, auser-input value, a value determined based on the weld settings, or anyapproximate speed.

In order to generate power at a higher frequency without damagingfrequency-dependent auxiliary loads 24, it may be desirable to provide acontrol scheme that prevents the engine speed from increasing when afrequency-dependent auxiliary load 24 is being utilized. For example,the system may be equipped with a proprietary auxiliary power socket inaddition to or in place of a standard auxiliary socket. Afrequency-independent auxiliary load may have a correspondingproprietary plug such that only frequency-independent auxiliary loadsmay be plugged into the auxiliary power socket. In the correspondingcontrol regime, then, the engine speed 56 may not be increased if poweris being drawn from the standard power socket but may be increased ifpower is being drawn from the proprietary power socket. In anotherembodiment, the controller may determine whether an attached auxiliaryload is frequency-dependent. The engine speed may be increased only ifthere is no frequency-dependent auxiliary load drawing power from thesystem. Furthermore, in another embodiment, the system may include powermanagement technology which regulates output voltage independent ofinput voltage, frequency, phase, etc. For example, Auto-Line™technology, available from Miller Electric, may provide such powerstability. The auxiliary sockets may therefore have regulated poweroutput, while the weld power output may be variable-frequency.

FIG. 10 illustrates a process 154 by which the trace 150 (FIG. 9) may begenerated. Referring to FIG. 2 for the system components, to FIG. 9 forthe graph 146, and to FIG. 10 for the process 154, the engine mayoperate at the operating speed 62 (block 156). That is, the welderand/or the auxiliary load may draw power from the generator. Using thesensors 36-42, the controller may determine whether power is being drawnfrom the weld power output and/or the auxiliary power output of thegenerators (blocks 158 and 162). If welding power is not being drawn(i.e., the welder is not being operated), and if a frequency-dependentauxiliary load is drawing power (i.e., a frequency-dependent device isbeing utilized), the engine speed 56 may be maintained at the normaloperating speed 62 (block 160). However, if welding power is being drawn(i.e., the welder is in use) and there is no frequency-dependentauxiliary load drawing power (i.e., no auxiliary device is in use, oronly a frequency-independent auxiliary device is in use), the controllermay increase the engine speed 56 to the higher speed 148 (block 164). Byincreasing the engine speed 56, the generators are able to output powerat a higher frequency. The welding gun 14 may operate more efficientlyusing the higher frequency power.

Finally, FIG. 11 illustrates a graph 166 of the engine speed 56 versusthe time 58 illustrated in accordance with embodiments of the presentinvention. Referring to FIG. 2 for the system 10 components and to FIG.11 for the graph 166, a trace illustrates the combination of multipleaspects of the present invention. For example, the engine may start atthe idle speed 60. At a time 170, the controller may detect a draw onthe generator by the welder. Based on preset operating parameters inputat the user interface, the engine speed 56 may ramp up quickly using thepreset-based control regime. At a time 172, as the engine speed 56approaches the target operating speed 62, the controller may switch tothe rpm-based control regime. The engine speed 56 may then stabilize atthe operating speed 62. After a time 174, the controller may determinethat neither the welder nor an auxiliary load is not in use and reducethe engine speed 56 to the idle speed 60. After no detected power drawfor a further time 176, the controller may reduce the engine speed 56 tothe low idle speed 102. Likewise, if no draw is detected after a time178, the controller may shut down the engine, effectively reducing theengine speed to the engine off speed 104. When a load is detected at atime 180, the controller may turn the engine on and ramp up the enginespeed 56 to the operating speed 62. Once again, the controller maytransition from the preset-based control regime to the rpm-based controlregime at a time 182. At a time 184, if the controller determines thatthere is not a frequency-dependent load on the engine (e.g., only thewelder is in operation, or the welder and a non-frequency dependentdevice are in operation), the engine speed 56 may be further ramped upto the higher speed 148.

It should be appreciated that any or all of the embodiments disclosedherein may be implemented in a single system, generator/welder, orgenerator. While only certain features of the invention have beenillustrated and described herein, many modifications and changes willoccur to those skilled in the art. It is, therefore, to be understoodthat the appended claims are intended to cover all such modificationsand changes as fall within the true spirit of the invention.

The invention claimed is:
 1. A method for controlling an engine-drivengenerator, comprising: monitoring a weld demand and an auxiliary demandfor output of a power generator being driven by an internal combustionengine; and increasing engine speed of the internal combustion engineabove a normal operating speed if the weld demand is detected and theauxiliary demand is not detected.
 2. The method of claim 1, wherein theincreased engine speed is a user-input engine speed.
 3. The method ofclaim 1, comprising reducing the engine speed to the normal operatingspeed if the auxiliary demand is detected.
 4. The method of claim 1,wherein welding presets determine a target speed, an idle speed, and aregime in which the internal combustion engine reaches the target speed.5. A method for controlling an engine-driven generator, comprising:monitoring a weld demand and an auxiliary demand for output of a powergenerator being driven by an internal combustion engine; classifying theauxiliary demand as frequency-dependent or frequency-independent if theauxiliary demand is detected; and increasing engine speed of theinternal combustion engine above a normal operating speed if the welddemand is detected and the auxiliary demand is not detected or isclassified as frequency-independent.
 6. An engine-driven generatorsystem, comprising: an internal combustion engine having a normaloperating speed and a maximum operating speed; a generator driven by theinternal combustion engine, wherein the generator is configured tooutput synchronous power at the normal operating speed of the internalcombustion engine; and a controller configured to increase engine speedof the internal combustion engine beyond the normal operating speed suchthat the generator outputs non-synchronous power only if an auxiliarydemand for power is not detected.
 7. The system of claim 6, wherein thesynchronous power has a frequency of 60 Hz and the non-synchronous powerhas a frequency greater than 60 Hz.
 8. The system of claim 6, comprisinga unique power outlet configured to limit use of the non-synchronouspower to external devices having a mating power connector that coupleswith the unique power outlet.
 9. The system of claim 6, comprising asynchronous power outlet and a non-synchronous power outlet.
 10. Thesystem of claim 6, comprising a selector having a first optioncorresponding to the synchronous power and a second option correspondingto the non-synchronous power.
 11. The system of claim 10, wherein thesecond option comprises an application having a higher amperage demandthan available with the first option.
 12. The system of claim 11,wherein the higher amperage demand is associated with a thickerelectrode of a torch, a thicker material to be worked on with a torch,or a combination thereof.